Decadal Decreases of Suspended Sediment Concentrations within the Yangtze River Estuary: A Response to Human Impacts

Changes in suspended sediment concentration (SSC) in an estuary have environmental, ecological, and social-economic implications. Under human impact, annual suspended sediment discharges into the Yangtze River Estuary YRE) display a downward trend, greatly influencing SSCs in the YRE. In this study, statistical analysis of SSCs measured in surficial water at 10 stations in the YRE indicates variations in decadal decreases in SSC, proven to be related to dam construction and soil conservation measures in the past decades. The degree of decrease varies temporospatially, with greater reduction in the annual surficial SSCs in the inner estuary than those in the outer estuary, and with the reduction rate in the former being greater in the dry season than the flood season, primarily because of the pronounced increase in water discharge during the dry season. In the outer estuary, the reduction rate in flood seasons is greater than in dry seasons because of the greater reduction in sediment discharge during the flood season. This study finds that SSC trends can be a useful reference for related studies of the YRE.